Lower accompaniment by one octave for #IV and V-VII chords.

AutoBand ignores input octave, so shift engine MIDI output by -12 for those chords (except drums) to keep the range from low #IV up to natural IV.

Co-authored-by: Cursor <cursoragent@cursor.com>

APP/app_tm1629.c

@@ -3,7 +3,7 @@
 static uint8_t  key_last = KEY_NONE;
 
 
-/* LED 期望颜色缓存：索引 = LedNum_TypeDef（0~7），COLOR_OTHER 表示灭 */
+/* LED ??????????¹×???? = LedNum_TypeDef??0~7????COLOR_OTHER ????? */
 //static LedColor_TypeDef led_cache[8] = {
 //    COLOR_OTHER, COLOR_OTHER, COLOR_OTHER, COLOR_OTHER,
 //    COLOR_OTHER, COLOR_OTHER, COLOR_OTHER, COLOR_OTHER
@@ -31,7 +31,12 @@ uint8_t app_tm1629_Scan_Key(void)
   if(key != key_last)
   {
     key_last = key;
-    LOG_I("KEY", "tm1629 key=%u", (unsigned)key);
+    if(key >= 1 && key <= 21)
+        LOG_I("KEY", "tm1629 key=%u pitch=%u type=%u", (unsigned)key,
+              (unsigned)chord_type_index_map[key].PitchOffset,
+              (unsigned)chord_type_index_map[key].type);
+    else
+        LOG_I("KEY", "tm1629 key=%u", (unsigned)key);
     TM1629_Handle(key);
     return key;
   }

MyCode/App_Auto.c

@@ -19,6 +19,64 @@ static uint8_t pStoreBuffer[PRESET_BUFFER_SIZE];
 //static uint8_t* pStoreBuffer;
 #define DEFAULT_TEMPO 100
 
+/* ======== 路线A：#IV 降八度拦截（音师库支持八度前的临时方案） ========
+ * AutoBand 库对输入音符只做音级识别，输出音区由其内部 octaveBase 决定，
+ * 固件侧在 GetChordNotesByType 里的低八度设计不可听。故在引擎输出回调处
+ * 按当前和弦状态对旋律通道做条件性八度偏移；音师新库到位后整体移除。 */
+#define CHORD_OCTAVE_INTERCEPT_EN   1
+#define DRUM_CHANNEL                9   /* 鼓通道不移调 */
+
+/* 当前生效的八度偏移（0 或 -12）。RAM 余量极小，不用按音符表：
+ * 状态翻转瞬间先向旋律通道补 CC123(All Notes Off) 清掉旧音区的音，
+ * 之后 NoteOff 统一按当前偏移还原即可，不会挂音。 */
+static int8_t s_chord_octave_shift = 0;
+
+static int8_t App_Auto_TargetChordOctaveShift(void)
+{
+#if CHORD_OCTAVE_INTERCEPT_EN
+    /* 与 GetChordNotesByType 的根音八度设计对齐（整段伴奏压一个八度）：
+     * V/VI/VII（键 13~21）根音本就在低八度（43/45/47）；
+     * #IV（键 10~12 + Pitch 升）整组低八度，为最低音。
+     * 引擎只认音级不认八度，故在输出侧统一补 -12。 */
+    if (KEY_ID_1629 >= 13 && KEY_ID_1629 <= 21)
+        return -12;
+    if (KEY_ID_1629 >= 10 && KEY_ID_1629 <= 12 &&
+        chord_type_index_map[KEY_ID_1629].PitchOffset == 2)
+        return -12;
+#endif
+    return 0;
+}
+
+static void App_Auto_QueueAllNotesOff(void)
+{
+    MidiFifoItem_t m;
+    for (int ch = 0; ch < 16; ch++)
+    {
+        if (ch == DRUM_CHANNEL) continue;
+        m.msg[0] = 0xB0 | ch;
+        m.msg[1] = 123;  /* CC123 All Notes Off */
+        m.msg[2] = 0;
+        m.msglen = 3;
+        mymidififo_InQueue(&m_MidiSendFifo,&m);
+    }
+}
+
+/* NoteOn 路径调用：偏移状态翻转时先清旧音，再返回新偏移 */
+static int8_t App_Auto_ShiftForNoteOn(void)
+{
+    int8_t target = App_Auto_TargetChordOctaveShift();
+    if (target != s_chord_octave_shift)
+    {
+        LOG_I("OCT", "shift %d->%d chord=%u pitch=%u",
+              (int)s_chord_octave_shift, (int)target,
+              (unsigned)KEY_ID_1629,
+              (unsigned)chord_type_index_map[KEY_ID_1629].PitchOffset);
+        App_Auto_QueueAllNotesOff();
+        s_chord_octave_shift = target;
+    }
+    return s_chord_octave_shift;
+}
+
 static void Func_CallBack_ProgramChange(int channel, int program)
 {
     MidiFifoItem_t midimsg;
@@ -32,8 +90,15 @@ static void Func_CallBack_ProgramChange(int channel, int program)
 static void Func_CallBack_NoteOff(int channel,int key)
 {
     MidiFifoItem_t midimsg;
-    midimsg.msg[0] = 0x80 | channel;
+    int out_key = key;
-    midimsg.msg[1] = key;
+    if (channel != DRUM_CHANNEL && key >= 0 && key < 128)
+    {
+        /* 按当前偏移还原；偏移翻转瞬间的旧音已由 CC123 清掉 */
+        out_key = key + s_chord_octave_shift;
+        if (out_key < 0 || out_key > 127) out_key = key;
+    }
+    midimsg.msg[0] = 0x80 | (channel & 0x0F);
+    midimsg.msg[1] = (uint8_t)out_key;
     midimsg.msg[2] = 0;
     midimsg.msglen = 3;
     mymidififo_InQueue(&m_MidiSendFifo,&midimsg);
@@ -43,9 +108,17 @@ static void Func_CallBack_NoteOff(int channel,int key)
 static void Func_CallBack_NoteOn(int channel,int key,int vel)
 {
     MidiFifoItem_t midimsg;
-    midimsg.msg[0] = 0x90 | channel;
+    int out_key = key;
-    midimsg.msg[1] = key;
+    if (channel != DRUM_CHANNEL && key >= 0 && key < 128)
-    midimsg.msg[2] = vel;
+    {
+        int8_t shift = (vel == 0) ? s_chord_octave_shift   /* vel=0 视同 NoteOff */
+                                  : App_Auto_ShiftForNoteOn();
+        out_key = key + shift;
+        if (out_key < 0 || out_key > 127) out_key = key;
+    }
+    midimsg.msg[0] = 0x90 | (channel & 0x0F);
+    midimsg.msg[1] = (uint8_t)out_key;
+    midimsg.msg[2] = (uint8_t)vel;
     midimsg.msglen = 3;
     mymidififo_InQueue(&m_MidiSendFifo,&midimsg);
 
@@ -135,6 +208,7 @@ static int Func_CallBack_ReadFlash(int address,int length,uint8_t* pOutput)
 //
 void App_Auto_Init(void)
 {
+    LOG_I("OCT", "intercept build 20260910 en=%d", (int)CHORD_OCTAVE_INTERCEPT_EN);
     AutoBandTop1_SetPresetStoreBuffer(pStoreBuffer,PRESET_BUFFER_SIZE);
     AutoBandTop1_Init();
     AutoBandTop1_RegisterCallBack_NoteOn(Func_CallBack_NoteOn);